GUANTANAMO BAY, Cuba, Jan. 21 -- The Obama administration faces a host of legal, logistical and diplomatic challenges in its plan to close the military prison here, and if the effort stumbles, it could bring steep political costs.

As the outlines of President Obama's intentions surfaced in a draft executive order Wednesday -- pledging the humane treatment of detainees and an end to torture, along with closure of the prison -- the difficulties ahead became equally clear.

Among them is the risk of politically explosive acquittals: Transferring cases out of Guantanamo raises the prospect that some may not stand up in court because of evidence tainted by torture or based on intelligence material that is inadequate in court.

If the administration were to create a new system of indefinite detention for some prisoners -- those considered too dangerous to release or impossible to prosecute, for example -- Obama could alienate part of his core constituency.

And if, as expected, some suspects are moved out of Cuba, even to the confines of a military brig in the United States, the administration is likely to face intense local opposition.

Some relatives of the victims of the Sept. 11, 2001, attacks were already dismayed by the suspension this week of the terrorism trials, believing that the existing process of military commissions is fair and that Guantanamo provides a secure location to hold and try terrorism suspects and enemy combatants.

"In his first official act as commander in chief, Mr. Obama has offered up the lives of almost 3,000 Americans on the ACLU's altar of political correctness and emboldened a ruthless enemy," said Donald Arias, who lost his brother Adam in the World Trade Center attack in 2001. "My brother will not be a sacrificial lamb on that altar."

The administration's plans are contained in an executive order calling for the "prompt and appropriate disposition of the individuals currently detained at Guantánamo," according to a draft copy obtained by The Washington Post. The order, which Obama is expected to sign imminently, states that the military prison should be "closed as soon as practicable, and no later than one year from the date of this order."

Officials will review the cases of the 245 prisoners who remain here to decide who can be released and who can be put on trial.

Officials must also decide in what legal setting the detainees should be prosecuted -- in federal court, military courts-martial, a revised system of military commissions or some combination of those courts.

Human rights groups welcomed the news of the executive order and the decision by a judge Wednesday to suspend the trials of five terror suspects, including that of Khalid Sheik Mohammed, the alleged mastermind of the 2001 terror attacks. That decision followed a request from the Obama administration and drew plaudits from Obama's supporters and international allies.

"To his last day, George Bush wanted to preserve the detention system he created in Guantanamo; meanwhile the 9/11 detainees wanted to die as martyrs of that illegitimate system," said Tom Malinowski, Washington advocacy director for Human Rights Watch. "This order repudiates Bush's legacy while denying Khalid Sheikh Mohammed his wish."

The draft executive order, in a section labeled "Humane Standards of Confinement," says that "no individual currently detained at Guantanamo shall be held . . . except in conformity with all applicable laws governing the conditions of such confinement."

It directs the secretary of defense to review conditions at the prison within 30 days.

Tuesday night, Defense Secretary Robert M. Gates received instructions from Obama and then gave guidance to "order a pause in military commission proceedings" while awaiting the outcome of a broader review of detention policy, according to a Pentagon official.

Military judges Tuesday suspended hearings for 120 days, following motions submitted by military prosecutors late Monday citing the "interests of justice."

"We expect there will be more detailed guidance coming from the president in coming days," said Bryan Whitman, a Pentagon spokesman. He said the Pentagon "has been examining any number of options" on where detainees may be moved, but "no decisions have been made."

The suspension halts until late May the trial of Mohammed and four other alleged al-Qaeda members, even though Mohammed and three fellow defendants objected to the delay.

Justice Department lawyers separately filed a motion in U.S. District Court in Washington on Tuesday asking a federal judge to delay proceedings in the habeas corpus cases of three Guantanamo detainees. The motion said that "the government is assessing how it will proceed" and needed more time to evaluate the cases. Attorneys for the detainees did not object, and U.S. District Judge Reggie B. Walton granted the request.

European allies, long concerned about Guantanamo, praised Obama's moves. Some, including Portugal and Germany, have expressed willingness to help close the prison.

In late December, in the last days of its presidency of the European Union, France initiated discussions on what European countries might do -- either resettling detainees or helping other countries do so, according to sources. European ministers are expected to discuss the matter in a meeting in Brussels on Monday.